The invention relates to a bi-stable apparatus for representation of a point of a tactile information, with a touch pin, which touch pin is axially displaceable between a lifted position, in which its touchable end projects over a touch surface, and a lowered position in which its touchable end does not project over the touch surface, and with two magnets, of which at least one is an electromagnet moving the touch pin and one moves a locking body which locking body is displaceable or shiftable from an inoperative position into an operative position, and reversely, in the inoperative position the locking body freeing the displacement of the touch pin into its lowered position, in the operative position the locking body blocking the displacement of the touch pin into its lowered position.
With one device of this type which is known from U.S. Pat. No. 3,987,438 and corresponding German Offenlegungschrift OS No. 2 407 452 (FIG. 1), the touch pin (10) is moved against the force of a return setting spring (24) into the set position (indicated by points) by the magnetic force which is exerted from a first magnetic coil (26) on its longitudinally displaceable core (12), in which set position, the touch pin is locked by means of a locking device, which locking device comprises a steel ball (28) and a second magnetic coil (44) with a core which is longitudinally displaceable in the coil. If the touch pin (10) is set, then, when the touch pin (10) has reached the set position, this ball (28) is pulled from the core (36) of the second magnetic coil (44), on which core a prestressed spring (50) engages, and by the magnetic field of the first magnetic coil (26) into the locking position, in which position the return path into its release position is blocked by the following core (36) of the second magnetic coil (44). In order to again transport the touch pin (10) into its cleared position (indicated in solid lines), the core (36) must be moved by the magnetic force produced by the second magnetic coil (44) against the force of the spring (50) engaging on the core into its release position, in which release position the core is locked by the steel ball (28), the steel ball being held fixed in this position by the core (12) of the first magnetic coil (26). For the setting as well as also for the clearing thus one of the two cores (12, 36) must be pushed into the other position by the magnetic force produced by the coordinated magnetic coil (26 and 44, respectively) against the spring (24 and 50, respectively), which spring engages on the core (12 and 36, respectively). Thus results in a relatively high energy requirement of the device. Moreover still with every change of the condition of the touch pin (10), the ball (28) of the locking device must be torn free from one of the two cores (12 or 36), which still increases the energy requirement. In view of the manufacturing expense, the multiplicity of the individual parts is disturbing, and with the assembly into arrangements with a multiplicity of touch pins it is practically impossible, to accommodate plug-in connections for all terminals or connections in the space which stands available, especially when between the touch pins the usual spacings are to be maintained with the representation of braille characters.
Also another device which is known from U.S. Pat. No. 3,987,438 or German Offenlegungsschrift OS No. 2 407 452 (FIGS. 2, 3) has a high energy requirement, a comparatively high manufacturing expense and a relatively large spacial requirement, which device differs from the previously mentioned body by another locking device. The end (154) of the core (112) of a first magnetic coil (126), which end is remote from the touch pin (110) as well as the end (158) which points to this core (112) of the core (136) of a second magnetic coil (144), which core (136) is arranged in alignment with this core (112), or of a permanent magnet are formed such that upon the setting of the touch pin (110), the magnetic force acting on the core (112) of the first magnetic coil (126) displaces this core (112) first into its longitudinal direction and upon reaching the set position turns it about its longitudinal axis. By this rotation the lower end (154) of the core (112) of the first magnetic coil (126) comes into a position in which it is held fixed by a step (159) on the upper end (158) of the core (136) of the second magnetic coil (144). Upon the transfer of the touch pin (110) from the set position (b) into the cleared position (a), the touch pin (110) together with the core (112) of the first magnetic coil (126) must first execute a rotational movement, so that it can become free of the step (159) and thereafter it can execute the translational movement providing the return stroke.